how to tell if hot water heater is full
Kristina Davis

Do you know how to tell if hot water heater is full? Is it possible to do so even if you don’t see the inside of your water tank?

While most modern systems are already equipped with visual aids, it’s still important to know and understand how much water you have inside the tank.

You will know that a water heater is already full when you turn on the hot water valve, and no remaining air is exiting the machine or the water heater.

Why It’s Important to Know If Your Tank or Heater Is Full

why important

To be straightforward, learning how to tell if hot water tank is full can give you a ton of different benefits and advantages.

Here are the reasons why it’s imperative to learn how you can identify if a hot water tank is already going over the recommended level.

There Could Be Sediments

At first, I honestly thought that leaving the hot water heater is the way to do it.

It’s a mediocre device that stabilizes the temperature of the water inside your home.

But, if you look at the scientific aspect of it, areas that have stale water are the breeding ground for sediments – moss, among others.

Mineral deposits, as well as other types of buildup, could appear in the inner walls and pipes of your hot water heaters.

They Could Not Operate Properly

not operate properly

Another factor why knowing the level of water inside your hot water tank would be operations.

Water heaters are devices that require water for them to operate properly.

For instance, if you have a large family and you guys need large supplies of hot water, then the level of water inside the tank should be enough.

If it is low, then the hot water it produces might not be enough.

Safety and Security

One cause for concern is safety and security.

In case you didn’t know, when the tank is full and is up to the temperature, the next pipe that’s coming out of the tank can be very hot.

For Flushing

for a flushing

Last, but most definitely not least is for you to know when you should flush it.

Take note, though, that it being full does not necessarily translate to you flushing it.

Flushing your hot water heater doesn’t always have to be done regularly.

But knowing if it’s full can guide you in the flushing process, particularly in terms of knowing when you should turn the tap off.

How to Tell If Hot Water Heater Is Full?

how to tell its full

Different hot water systems have different ways of letting you know that level of water inside the tank is enough.

So, to help you understand it a bit more and deeper, here are the different ways of identifying water levels inside your water tank.

Checking Visual Aids

As I mentioned above, you’ll find newer and more modern models of hot water heaters equipped with visual aids to help you identify your tank’s water level.

Visual aids vary from one manufacturer and model to another. Don’t expect them to be, all the same, they wouldn’t!

This is true especially if they are made by different brands and suppliers.

So, what you want to do is check the user guide or manual of your water heater to know how you can identify its water level.

You can also make use of the stickers attached to it for guidance.

Digital Screen

the digital screen

The more advanced and high-tech pieces of machinery have digital screens that can display different information regarding your tank.

Moreover, this is also the component where you can check the current water level of your tank to identify if it is already full.

These types of hot water heaters are the ones used in hotels – unless you have this in your house, this probably is the easiest and simplest way to do it.

Manual Checking

Last, but most definitely not least is for you to check it manually.

Most hot water heaters are made of stainless steel, so you wouldn’t really be able to see through them.

Fret not – here’s a simple, yet proven way of checking and identifying whether your hot water heater is full or if it still has room!

manual check

To check and identify if your tank’s water level is full, first, turn on the tap for hot water. Then, leave it on for a while – about a few minutes.

After that, twist the tap off to stop the flow of water. Lastly, turn it on again, and check if there’s air that comes out.

If there is no air coming out, then the heater is already full.

The presence of air and pressure is an indication that there’s still room inside the hot water tank.

You can use this information to be aware of the situation of your hot water heater.

In case you want to know how to tell if the hot water tank is full, then this is it!

My Hot Water Heater is Full, What Should I Do?

what should i do

If it’s full and you haven’t had the chance to check it before, then it probably has been full for a while now.

So, what do you do? Simple – flush it or drain it, then replace it with new water.

The following are the primary reasons why you want to flush it:

  • There could be rust in the entire house’s water supply
  • Foul smell and odors coming out of the showers and faucets
  • Discoloration of water when you set it to hot water

How to Drain Hot Water Heater?

drain water

Here’s how you can successfully and properly drain a hot water heater:

  1. Turn the power supply off (both hot and cold water).
  2. Then, turn a hot water tap inside the home to let air into the tank.
  3. Connect a hose or a pipe to the tank’s valve.
  4. Position the other end of the hose to the drain on the floor.
  5. If you don’t have one, direct the other end to a bathtub or a heatproof bucket.
  6. Once done, turn on your drain valve.
  7. Then, turn the water supply (cold) on and keep it running for at least 5 minutes.
  8. Turn the drain valve off when the water is clear.
  9. Turn the tap off when the tank is completely filled up.
  10. Reinitialize the power supply going to the hot water tank/heater.
As a general rule, homeowners are advised to flush their water heaters once every five to six months for a household of 3 to 4 people. 

If you have more than 5 people in the house or if you have a big family, flush it at least once every three to four months.


popular questions about heater

Here are a few other important things to note in identifying whether you have a hot water heater that is full or not.

How Long Does it Take For My Hot Water Heater to Fill Up?

There’s actually no specific time for hot water heaters to fill up, and this is due to the fact that different tanks have different sizes.

In approximation, though, 80-gallon tanks can take anywhere between 30 and 40 minutes to fill, while 40-gallon tanks can take anywhere from 20 to 30 minutes.

How Do I Know If My Hot Water Heater is Failing?

The most obvious signs that you have a bad hot water heater would be if there’s leaking from the heating tank.

If the water pressure is low, and if there’s an inconsistent temperature fluctuation in the shower (both hot and cold).

Why Does My Hot Water Run Out so Fast?

The hot water on your tank runs out quickly because of sediments forming at the bottom of the tank.

Anything from sand, rust, silt or loose minerals can situate at the inside bottom part of the tank, which can make your hot water run out faster and quicker than it should.

The Bottom Line

Now, if you’re trying to look for accurate information on how to tell if hot water heater is full for personal reasons, this is how you do it!

Hot water heaters have been an integral part of homes, especially during the winter season.

You don’t need to worry or think about it if your tank has visual indicators – but what if you don’t?

Check it manually so you’re armed with this skill that you can use wherever you go!